Regeneration of perchlorate (ClO4-)-loaded anion exchange resins by a novel tetrachloroferrate (FeCl4-) displacement technique

Selective ion exchange is one of the preferred treatment technologies for r emoving low levels of perchlorate (ClO4-) from contaminated water because o f its high efficiency and minimal impact on water quality through the addit ion or removal of chemicals and nutrients. However, the exceptionally high affinity of ClO4--for type I anion-exchange resins makes regeneration with conventional NaCl brine extremely difficult and costly for practical applic ations. The present study entails the development of a novel regeneration m ethodology applicable to highly-selective anion-exchange resins. Tetrachlor oferrate (FeCl4-) anions, formed in a solution of ferric chloride and hydro chloric acid (e.g., 1 M FeCl3 and 4 M HCl), were found to effectively displ ace ClO4- anions that were sorbed on the resin. A mass-balance analysis ind icated that a nearly 100% recovery of ion-exchange sites was achieved by wa shing with as little as similar to5 bed volumes of the regenerant solution in a column flow-through experiment. There was no significant deterioration of the resin's performance with respect to ClO4- removal after repeated lo ading and regeneration cycles. Thus, the new methodology may offer a cost-e ffective means to regenerate ClO4- -loaded resins with improved regeneratio n of efficiency, recovery, and waste minimization in comparison with conven tional brine regeneration techniques.